Apparently, reading an excerpt in a book review (when it first came out) made a lasting impression. Below are two paragraphs from Joseph Alsop's memoirs (more of which, though of course not the whole book, can be read at Amazon.com). (I'm ordering a copy of the book, but it will take a while to arrive.)

Not that I expect ever to taste it myself, but could anyone describe the taste better than Alsop? Opinions about whether the disappearance of this dish is a great loss?

Rich

"To these basics were added delicacies: shad in season, not boned but so slowly cooked in a sealed container that the bones melted, giving it ten times the taste of the flannellike fish we get today; shad roe in mountains; soft-shell crabs; oyster crabs, which are tiny parasite crabs that inhabit oysters and have the taste of both animals, not exactly in mountains because they were too expensive, but as a recurrent prize dish; in the autumn, turkey broilers (meaning specially fed, very young turkeys that were literally small enough to split and broil); reed birds, the pride of southern houses; all sorts of game birds one sees no more like plovers and wild turkey; and there was, above all, terrapin in season.

"This creature---halfway between a sea turtle and a land tortoise---was, to me, the greatest of American delicacies, and since it had inhabited the Maryland estuaries in great numbers, it became a staple of grand Washington dinners. Properly made (without cream sauce), terrapin appeared on the dinner table as an unctuous, even gelatinous stewlike dish, with the tenderest bits of the terrapin's meat plus its liver and the female terrapin's eggs all floating gently in an enormously rich sauce made by endlessly boiling down the broth derived from the rest of the terrapin, plus fresh butter in huge quantities, sherry and cayenne pepper. I don't know how to describe the taste except to say that although its aroma reminded one a bit of the way feet sometimes smell, it was absolutely delicious."

I've dined on terrapin soup only twice - once during a meal served in 1959 when I was in the Marines, the meal hosted at the dining room of the Joint Chiefs of Staff (in the Pentagon) and once more recently (about a decade ago) at a graduation ceremony held at the Annapolis Naval Academy. Coincidence only that both were associated with the military, but in both cases no coincidence as to excellent.

Deeply aromatic (but not feet as some say), leaning to the herbal notes inherent to the meat, bursting with natural salt-water and pepper typical of the terrapin and flavors that lingered on and on. In both cases ideal with firmly crusted bread.

A good chance that you may never taste it. I believe terrapin is now a protected species. Indeed, other kinds of turtle soup, each however with the special caracteristics of the region. Especially popular in fine restaurants in Hawaii, Japan and parts of Thailand.